This invention relates to data recording and in particular to a novel improved multi-disk arrangement for data recording.
Workers in the art of generating and/or utilizing magnetic recording media are aware of the various forms it takes; in the case of digital recording these forms have historically comprised drums, disks and tape in various configurations. Each medium has its own advantages and shortcomings depending upon the application. For instance, magnetic drum records facilitate relatively good data compression (high data density) and fast access time; however, they are relatively expensive to provide and are not generally suitable for "archival" storage of data. Magnetic tape, on the other hand, is comparatively inexpensive and is highly suitable for "archival" storage; however, it must be accessed serially (not randomly) and relatively slowly.
Magnetic disk storage is intermediate in access speed, facilitates random access and, in many cases, is particularly well suited for storage of "open-ended" data field (i.e., of indeterminate length). Disks -- especially "flexible disks" -- can serve as a "unit record" medium that is compact, light, and is readily transported, stored, and handled, interchangeably with other like disks. Accordingly, magnetic disk media are now finding widespread favor, especially in the data processing arts and are currently manufactured and used in great volume and in several forms. With todays high-volume disk usage, any reduction in disk cost looms highly significant, as workers in the art know. This invention facilitates high-volume/low-cost disk usage, teaching a novel multi-disk organization, allowing a pack of disks to be handled as a single record unit.
Recently a step toward cost reduction appeared in the form of the flexible, or "floppy", magnetic disk. Floppy disks can be fashioned from the same polyester sheet material as magnetic tape (e.g., the familiar polyethylene terephthalate), with a magnetic coating thereon -- this plastic being simply cut into the shape of a circular disk with a central mounting hole to accommodate the familiar drive-spindle. Such a "prior art" floppy disk is well known to workers and is shown in FIG. 1; a conventional envelope, or jacket, therefor is illustrated in FIG. 2.
The present invention is directed toward improving the design of such flexible magnetic disks as adapted for collection into a ("floppy") pack, -- something new in the art -- with any disk surface thereof being adapted for selection, and the pack accordingly "partitioned" or split, by automatic means. That is, with such a "floppy disk pack", the invention is particularly adapted to facilitate automatic partitioning of the pack to expose any selected disk surface for Read/Write operations -- using surprisingly simple means and methods as described hereinafter.
Workers will recognize that there are many advantageous uses for such "floppy disk packs", for instance, they offer enhanced volumetric effeciency of data storage -- that is, a maximal number of data bits may be stored in a given volume with a floppy disk pack, the disks being so thin (e.g., on the order of a few mils thickness) and so compliant as to pack closely together. --prior efforts with flexible disks:
Workers have suggested that in certain instances, disks may be assembled into a flexible multi-disk file, with one or both sides treated to record data bits in the form of magnetic signals as is well known in the art. One problem, however, has been the preconception that one must house such flexible disk packs in a rigid containment structure. Also no simple, practical way has yet been found to access an individual selected recording surface in a precise, rapid and repeatable manner -- principally because these "floppy" substrates are so difficult to stabilize mechanically. Now, workers well know that it is no easy task to precisely position a Read/Write head between two tissue-thin floppy disks separated by only a few mils, and to do so quickly and simply. And, with such a floppy disk file, dimensional instabilities and variations (e.g., varying thermal effects, manufacturing tolerances) are to be expected, as workers know. Then, even if one is able to hold each disk in a pack at a constant reference position relative to the other disks, transducer access and positioning is still problematical.
Accordingly, workers have resorted to special means, heretofore, for packaging and accessing floppy disk recording surfaces. For instance, "floppy" disks were thought to require support, while rotated (for recording) also, it was assumed they would suffer undue surface wear from frictional effects when stacked contiguously. Accordingly, workers have avoided stacking them directly in contact, i.e., "one-upon-another". Also, getting head-access to superposed floppy disks has seemed an impossible task. This invention is adapted to facilitate such contiguous stacking without compromising either disk integrity or access convenience. --prior art "floppy-disk" handling:
One approach, shown in U.S. Pat. Nos. 3,509,533 to Krijnan and 3,618,055 to Van Acker, involved an enclosed pneumatically pressurized chamber, with the flexible disks being stacked in spaced relation on a common spindle. These disks were perforated with holes to facilitate "pumping" of air through the stack and the associated spindle was "slotted" and adapted to control air flow from the center, radially outward, and thereby facilitate disk manipulation.
With recording density being an inverse function of head/disk spacing, many arrangements have been suggested to facilitate the close "following" of the disk surface by a transducer head. In an early approach (see U.S. Pat. No. 2,950,353 to Fomenko), the air flow was manipulated to facilitate transducer/disk engagement at high speed for high density magnetic recording. Similar arrangements with pliant flexible disks are disclosed in U.S. Pat. Nos. 3,153,241; 3,225,338; 3,369,227 and 3,573,771 also certain flexible disk designs are indicated in U.S. Pat. Nos. 3,678,481 and 3,668,658; while various forms of a flexible disk file are indicated in U.S. Pat. Nos. 3,867,723; 3,810,243; 3,852,820 and 3,838,462.
Workers are also familiar with various means for accessing multi-disk files by means for displacing the (otherwise-inaccessible) facing recording surfaces while the disk stack is rotating, to provide clearance for entry and manipulation of a transducer assembly. For instance, a "sliding-transfer" arrangement is disclosed in U.S. Pat. No. 3,130,393 to Gutterman (who employs pressurized air to "slide" the disks apart) and in U.S. Pat. No. 2,960,340 to Seidel (phonograph records slid relative to one another by probe means). But, as workers realize a floppy disk file responds poorly to the "forced-piston" motion contemplated by the Gutterman arrangement. --problems addressed:
Thus, certain problems come to mind when one contemplates manipulating a floppy disk file. For instance, they have not proven as reliable or durable as desired; the thin pliable disk can be somewhat fragile, especially when subjected to extreme physical hazards, such as sliding contact or impact with a sharp-edge like a "separator knife" or a transducer access arm. While the cost of the disk is relatively inconsequential, the data stored thereon is often invaluable and could be defaced by such contact. The present invention is designed to alleviate or eliminate the risk of such destructive contact, and particularly to teach the partitioning of a disk pack without employing "penetrator knives" as heretofore proposed.
Also, with the increased popularity and use of floppy disk media, it has become especially important to emphasize disk pack features like ready "removability" and record "interchangeability", as well as increased bit density and cost effectiveness (e.g., increasing data density per cm.sup.2 and data capacity per disk spindle, increase in data rate, reduction in access motion and rotational delay, improved data reliability and lower cost per M-byte). Indeed the desire for unit record removability has led to much of the increased use of (single) flexible disks -- e.g., cartridges with a disk packaged in a jacket like that indicated in FIG. 2. Now, such "removable media" can offer many advantages to the user -- for instance, the ability to exchange data-set libraries between applications, the availability of data-set backup and security, and the interchange of data records among alternate drives and systems. The lightweight, compactness of floppy disks even allow these records to be conveniently mailed between stations, using ordinary postal service. This invention enhances these advantages while also vastly increasing the data capacity of a disk cartridge.
Data removability, is, however, not without its price -- e.g., the cost of disk-loading hardware, of disk packaging (cartridge) means for protection against contamination and for security and the cost of of the head-carriage retraction mechanism and control electronics involved, and especially of the means for aligning Read/Write heads with a selected disk track. Such "trade-off" considerations can deter use of removable disk records -- but with the invention this is not likely to be so. That is, the present invention is directed toward providing improved multi-disk records, and disk packs, adapted to meet the foregoing problems and objectives in a manner satisfying minimum-cost objectives. The invention maintains the convenience of the removable floppy disk, while packaging a number thereof in a relatively convenient unit record file.
The foregoing and other features, objects and advantages according to the present invention will be more fully appreciated and become more apparent upon consideration of the following description of preferred embodiments, taken in conjunction with the attached drawings, wherein like reference indicia denote like elements.